But wait: we already had carbon-containing molecules on Earth, and we have no idea what molecules Philae found. The cometary compounds could, for example, be methane (a simple molecule with one carbon and four hydrogen atoms)—a molecule unlikely to have played a major role in the origin of life. Ditto for carbon monoxide or carbon dioxide (CO and CO2 respectively). The early Earth alreadyhad carbon in those molecular forms in the atmosphere, so why did we need to get them from a comet or asteroid? There were also physical forces on Earth, like heat and pressure around thermal vents, that could…